Loom

ABSTRACT

A loom having a warp letoff mechanism with a warp beam, a fabric takeup device with a pulling cylinder, a batten, a transmission positively driving the warp beam from the batten, and a regulator responsive to the difference between the speed of the thread being unwound from the warp beam and the speed of the pulling cylinder and acting on the transmission. Thus the loom has a constant ratio between the length of the fabric being produced and the length of the unwound warp from the warp beam.

United States Patent [72] Inventor Omer Vandoolaeghe [56] References Cited Comines, Belgium UNITE [21 Appl. No. 756,903 D STATES PATENTS [22] F] 2,303,297 11/1942 Budzyna et a1. 139/99 i ed Sept. 3, 1968 2,888,955 6/1959 Kondo 139/99 [73] Assignee Rog Decramer ari'wa ler 139/99 wervik, Belgium FOREIGN PATENTS [32] Priority Sept. 4, 1967 626,901 3/1936 Germany 139/99 [33] Belgium 24,106 1898 Great Britain 139/99 1 703,433 Primary Examiner-James Kee Chi Attorney-Stevens, Davis, Miller & Mosher LOOM ABSTRACT: A loom having a warp letoff mechanism with a 3 Claims, 5 Drawing Figs warp beam, a fabric takeup device with a pulling cylinder, a batten, a transmission positively driving the warp beam from [52] US. Cl 139/99, the batten, and a regulator responsive to the difference 139/304 between the speed of the thread being unwound from the warp [51] Int. Cl D03d-49/06, beam and the speed of the pulling cylinder and acting on the D03d 49/20 transmission. Thus the loom has a constant ratio between the [50] Field of Search 139/99, 97, length of the fabric being produced and the length of the un- 100, I09, 1 10, 304, 307, 308 wound warp from the warp beam.

l2 A a l R 16 34 l9 to f 6 I7. 9 6b It? I I/ a 'K 1 a 9O 60 I/ c 6c '5 I 50 2 b PATENTEDFEB EH97! 3.551.497

sum 1 nr 2 INVENTOR 23b OMER VANDOOLAEGHE 29 3| J; i I BY 3 S mmm lw ATTORNEYS ,PATENTFD FEB 9 19m SHEET 2 or 2 INVENTOR OM ER VAN DOOLAEGHE MM: $241k ATTORNEYS LOOM In the known warp unwinding devices, the thread-bearing roller forms some kind of lever which is swingable about a bearing point fixed to the loom frame. For this purpose, the thread-bearing roller has in some looms a cross section with an elongated shape. This roller may then swing about an axis located in the lower part thereof. In other cases, the threadbearing roller is attached on either side to the upper part of two parts which are more or less elongated. These parts are swingable about a shaft that passes through the lower portion thereof and which is connected to the loom frame. To the shaft about which the thread-bearing roller is swingable or to the lower part of the roller itself in the first case, or to the lower portion of one of the parts in the second case, is attached at least one arm which leads away from the heddles. From the free end of this arm hang one or several weights. Such weights cause the thread-bearing roller to swing in such a way that this roller lies as far away from the heddles as possible. Thus, the warp threads are stretched. That arm the weights hang from, is also connected to the mechanism for rotating the beam. A swinging of the thread-bearing roller and thus of the arm, which corresponds to a raising or lowering of the arm end, thus influences the mechanism that rotates the beam.

In most known looms, the mechanism that rotates the beam comprises a rod which is rotatably fixed to the loom batten. This rod is connected at the other end to a pawl. By an alternating motion of the rod, this pawl rotates a ratchet wheel. This wheel is fixed on a shaft a portion of which forms a worm. Such worm rotates a gear wheel which is fixed on the beam shaft. In this way, the swinging movement of the batten causes the beam to rotate. In the known looms of this kind, the above-mentioned arm to which one or several weights are hung, is connected by bar to the said rod. When the speed of the thread-bearing roller is higher than the normal speed, that is the speed thereof which results in a linear warp speed corresponding to the linear fabric speed, corrected for the warp shortening by the weft, the warp will get shorter. The threadbearing roller will swing and come nearer'to the heddles. The arm end will thus be raised. As such end is connected by a bar to the rod, said rod will also be raised. The pawl at the end of this rod will lie at some time higher than the ratchet wheel. The alternating motion of such rod with its pawl will no longer cause rotation of the ratchet wheel. The beam will stop. The speed of the thread-bearing roller will consequently become slower than normal. The warp will get longer and the threadbearing roller will swing. The arm end will go down as well as the rod end with the pawl. This pawl will again cause the ratchet wheel and thus the beam to rotate.

This warp unwinding device with regulation of the unwinding speed by means of arms on which weights are hung, has serious drawbacks. Indeed, when the heddles open the warp to let the shuttle pass through, this warp is shortened. By means of the arm and the thread-bearing roller, the weights attached to this arm will exert a stronger pull on the warp, while the opposite should occur. The action of these weights will thus make it more difficult to open the warp by means of the heddles. The reverse occurs when the heddles close the warp. This periodical lengthening and shortening of the warp causes the regulating mechanism to operate each time. Besides, each time the reed beats the pick, the warp undergoes a small sudden movement. By each sudden movement, the weights will jump. Moreover, it is nearly impossible to find the ideal weight to be used for some particular warp shortening by the weft. When the weight is too light, the arm will swing too much and the arm will not go down fast enough when the warp is getting longer. On the contrary, if the weight is too heavy, the warp will be stretched exceedingly when it becomes shorter. The arm end will thus not go high enough. In both cases, the speed regulating will fail.

Due to these drawbacks, it is obvious that such with such a warp unwinding device, the fabric will not be quite regular.

This invention has for its object to obviate these drawbacks and to provide a warp unwinding device which is rather simple and which always give a constant ratio, dependent on the warp shortening by the weft, of the warp unwinding speed to the fabric winding speed. In that case where there is no warp shortening, this ratio is 1, while in the other cases this ratio is larger than 1. As the device does not make use of weights, the warp tension is not too high, in such a way that the heddles can open easily the warp.

For this purpose, the device comprises at least one shaft, at least one element fixed on this shaft and fast relative thereto, at least one movable element which is threaded thereon and which may move along a direction in parallel relationship with the shaft rotating axis, part of the unit formed by the shaft and the element fixed thereon being connected by a transmission to one of both parts formed by the thread-bearing roller and the cylinder the fabric partly passes around, the movable element being connected by a transmission to the other one of both parts, one of the two above-mentioned elements lying on the shaft being provided on a surface in substantially parallel relationship to the rotating axis of the shaft with at least one notch which extends along a direction at an angle to the rotating axis, while the other element has at least one element contacting at least one portion of the shaft movable element and at least one portion of the beam-rotating mechanism, this element converting a displacement of the movable element along a direction in parallel relationship with the shaft rotating axis into a displacement of that portion of the mechanism, this displacement infiuencing, at least as soon as some value is exceeded, the operation of the beam-rotating mechanism.

According to a particular embodiment of the invention, the beam-rotating mechanism comprises a bar which is rotatingly attached to the loom batten and which is connected to a pawl which, during part of the alternating movement of the bar, may rotate a ratchet wheel fixed on a rod which is at least partly screw threaded, the threaded portion of which meshes with a gear wheel attached to the beam, while that element which engages the shaft movable element is formed by a lever which has a bearing point on a part fixed to the loom frame and which contacts by one end thereof the shaft movable element and which, by the other end thereof, straddles the bar in such a way that a displacement of the movable element, in parallel relationship with the shaft rotating axis, causes a displacement of such bar.

According to an advantageous embodiment of the invention, that element which engages the movable shaft has at least one part which is somewhat in the shape of a two-prong fork which surrounds partly a portion of the movable element between two projecting portions of this element, said part being rotatingly attached to the element remainder.

In another preferred embodiment of the invention, that transmission which connects one part of the unit formed by the shaft and the element fixed thereon to one of the two parts formed by the thread-bearing roller and the cylinder the fabric partly passes around, and that transmission which connects the movable element to the other one of said two parts, are metal chain drives, one portion of the movable element forming a sprocket while a sprocket is attached to the thread-bearing roller, to the cylinder the fabric partly passes around and to the unit formed by the shaft and the element fixed thereon.

Other details and features of the invention will stand out from the description given below by way on nonlimitative example and with reference to the accompanying drawings, in which:

FIG. I is a diagrammatic side view of a loom according to the invention;

FIG. 2 is a detail side view of part of the loom shown in FIG.

FIG. 3 is a front view of that part of the loom shown in FIG. 2, with the structure of the slot 2b omitted for the sake of clariy;

FIG. 4 is a section along line 4-4 of FIG. 3; and

FIG. Sis a section along line 55 of FIG. 3.

In the FIGS. the same reference numerals pertain to similar elements.

The loom as shown in the drawings, comprises essentially a beam 1, a mechanism for rotating said beam and a regulator which regulates the unwinding speed.

The beam-rotating mechanism comprises first a bar 2 which extends along a direction in parallel relationship to the sidewall of the loom. Said bar 2 is comprised of two parts: one part with circular section and one part with rectangular section. By the end of the circular section part, said bar 2 is connected to the batten 3 of the loom adjacent the pivot point 3a thereof. This bar may however swing relative to this batten. The left end 2a of the bar 2 passes therefor through a slot 2b provided in a part which is fixed relative to the batten, while a nut is arranged on such end. During the loom operation, the batten 3 swings about the pivot point 3a thereof. The bar 2 will then perform a reciprocating motion in parallel relationship with the loom sidewall. The rectangular-section portion of said bar 2 is provided with a rectangular cutout 2c which opens downwardly. By means of a bolt 4 the lengthwise axis of which is parallel to the axis' of the bar 2, and which passes through the free end of the rectangular-section part of said bar 2 into the rectangular cutout, one may adjust the length of said cutout. Through this cutout, the bar 2 is secured to a part 5. Said part 5 is slipped over a partly threaded shaft 6. Said shaft is attached in a somewhat vertical attitude to the loom frame by two bearings 6b and 6c. The part 5 is rotatable about the shaft 6. As shown in FIG. 4, the part 5 is of more or less round shape with two arms 5a and 5b extending at right angles to shaft 6. This arm 5a is somewhat in the shape of a rectangle with that corner 5c farthest away from the batten cut back. THe width of this arm 5a is thus reduced towards the free end thereof. The bar 2 is anchored to said arm 5a, that is the end of the bar 2 bears on such arm 50. To avoid slipping of the bar, that part 5b of the arm 5a against which the bar 2 bears, is slightly a A pawl 7 is fixed by a pivot pin 7a to arm 5b of part 5 and is biased against a ratchet wheel 8 by a spring 7b. During part at least of the movement of the bar 2 along one and the same direction, the pawl 7 drives the ratchet wheel 8 and rotates the shaft 6 by engagement with the portion 6a formed as a worm gear. With the shape of the teeth and the position of the pawl as shown in the FIGS. the wheel 8 will rotate whenever the bar 2 moves towards the beam. During the movement of the bar 2 in the opposite direction, the pawl will move relative to the wheel 8 without driving same. The gear wheel 9 is attached to the shaft 90 which supports the beam 1 and thus rotates about the same rotating axis. The thread of the worm 60 must be correctly directed to rotate the beam 1 so that the warp thread la is unwound. In the FIGS. the beam must rotate clockwise. The swinging movement of the batten 3 thus causes a discontinuous rotating motion of the shaft 6 and worm 6a and thus, through the worm gear 9, of the beam 1.

This mechanism for rotating the beam 1 is controlled by a regulator R according to the'invention. This regulator affords a constant ratio between the linear speed of warp unwinding and the linear speed of fabric winding. Both these speeds are measured as follows: after leaving the beam, the warp passes over the thread-bearing roller 33 and partly surrounds the same. The rotating speed of this thread-bearing roller will thus be directly proportional to the warp linear speed. On the one end of this thread-bearing roller is attached a sprocket 10. Said sprocket 10 has a number of teeth which is equal to the number of centimeters in the roller circumference. This number has for instance a value of 36. Over this sprocket 10 passes a metal roller chain 11 that connects same to the regulator R. Beyond the thread-bearing roller 33, the warp passes through the harness with the heddles 12. The heddles 12 have been shown diagrammatically in FIG. 1. These heddles open the warp to let the shuttle go through, after which they close the warp. The batten 3 together with the reed 13 thereof pushes the pick against the preceding picks. The warp, which has now become a fabric, passes over a breast beam 14 and about the pulling cylinder 34. Said cylinder 34 is moved directly, or through a transmission, by a motor (not shown). The fabric is moved forward by said pulling cylinder. This cylinder 34 also rotates the sheave 15 by pressing against same. The fabric is wound about said sheave 15. To have a contact area between the pulling cylinder 34 and the fabric as large as possible, the fabric must pass over a roller 16 before being wound. The rotating speed of this pulling cylinder 34 is thus directly proportional to the linear speed of the fabric. At one end, on that same side of the loom where the sprocket 10 is located, a sprocket 17 is attached to this pulling cylinder 34. Said sprocket 17 has a number of teeth equal to the number of centimeters in the circumference of the pulling cylinder, in that case where there is no warp shortening by the weft. To obtain a warp shortening, as explained below, teeth must be added to the sprocket 17. This sprocket is thus easily replaceable. For the case where there is no warp shortening, the number of teeth is for instance 42. Over this sprocket 17 passes a roller chain 18 that connects this sprocket to the regulator.

The regulator R is comprised of a shaft 19 each end of which passes through a hole into one arm of U-shaped bracket 20 fixed to the loom frame. On the rotating shaft 19 are fixed two elements 21 and 22. These elements are fast relative to the shaft. Between these two wheels is arranged an element 23 which is movable relative to the shaft 19. This element 23 is comprised of four cylindrical portions, 23a, 23b and 23c to be described hereafter. Element 23 may rotate with a rotation speed different from the shaft 19 and may also move axially on the shaft between the wheels 21 and 22. Element 21 is a sprocket wheel which is secured to shaft 19 by a setscrew 27 and which has for instance 13 teeth. Over this sprocket passes the chain 18 from the sprocket 17 which rotates together with the pulling cylinder 34. The shaft 19 will thus have a rotating speed proportional to the rotating speed of the pulling cylinder 34. The fixed element 22 is a cylinder with a diameter larger than the sprocket forming part of element 21 and is secured to the shaft 19 by setscrew 270. On that wall of this element farthest away from the rotating axis, a part 24 of rectangular shape is fixed by bolts. The lengthwise axis of this part 24 is in parallel relationship with the rotating axis of the shaft 19. This part extends with respect to the element 22 on the side of the element 21. Adjacent the free end of this part is fixed a bolt 25 with a nut 26. The head of such bolt is directed towards the rotating axis of the shaft 19. The fixed elements 21 and 22 are attached to the shaft 19 by screws 27. The movable element 23 consists of a sprocket 23a, cylindrical portion 23b and a cam 23c. The sprocket 23a is identical in diameter and number of teeth to the sprocket 21. Sprocket 23ameshes with chain 11. The rotating speed of the element 23 is thus directly proportional to the rotating speed of the thread-bearing roller 33. Integral with sprocket 230 are two cylindrical portions 23b and 23c. The center cylindrical portion 23b has a smaller diameter then the diameter of that cylindrical portion 230 which is farthest. away from the sprocket portion 23a. Portion 230 has a smaller diameter than the diameter of element 22. On the outside circumference, this last cylindrical portion is provided with a notch 28. This notch 28 is in the shape of a groove 28 with a rectangular cross section the width of which is equal to the width of the head of the bolt 25. This bolt forms a projection which comes to lie into this groove. The axis of this groove which extends through the width of the cylindrical portion is at an angle to the rotating axis of the element 23. The direction of the axis of said groove 28 is such that when the groove lies at the top, as it comes nearer the wheel 22, it at the same time comes nearer the thread-bearing roller 33.

The regulator as described above is connected to the beamrotating mechanism through a lever 29. This lever 29 is rotatable about a fixed pivot 29a secured to the loom frame. The rotating axis of this lever 29 is in substantially parallel relationship with the axis of the bar 2. This lever is more or less vertical. The the lower end thereof is fixed an element 30 that forms a two-pronged fork which grips the roundsection portion of the bar 2. Both prongs of the fork 30 thus lie in a plane at right angle to the rotating axis of the lever 29. To the upper end of this lever 29 is attached to a yoke 31 which is rotatably secured by nut 32. This fork 31 partly surrounds the smallerdiameter cylinder 23b of the element 23. This yoke 31 thus extends in a plane parallel to the pivot axis of the lever 29. Such yoke 31 may thus swing somewhat relative to this lever 29.

Regulator R operates as follows: the sprockets and 17 rotate in the same direction, the shaft 19 and the element 23 will also rotate in the same direction. When the rotating speed of the shaft 19 and thus the rotating speed of the fixed elements 21 and 22, i s equal to the rotating speed of the element 23, such movable element will be stationary relative to said elements 21 and 22. On the other hand, if this rotating speed is not the same, the movable element 23 will move along the shaft 19 between the elements 21 and 22. When the rotating speed of the element 23 is faster than that of the shaft 19, said element 23 will rotate somewhat relative to the elements 21 and 22 in the same rotating direction. That portion of the element 23 with the groove 28 will thus move relative to the bolt 25. Since this groove 28 is a portion of a helix, this movement of the element 23 relative to the bolt 25 will cause an axial displacement of element 23 in the direction of the sprocket 21. When however the element 23 rotates more slowly than the shaft 19, the element 22 will rotate relative to the element 23, along the rotating direction. The projection 25 will push against the walls of the groove 28 and move the element 23 axially towards the element 22. Each axial movement of the element 23 causes an equal movement of the yoke 31 and the lever 29, as well as to a displacement in the opposite direction of the fork and thus of the bar 2. In that case where the element 23 comes nearer the element 21, which corresponds as mentioned above to a rotating speed of the element 23 which is faster than that of the shaft 19, the fork 30 will move away from the loom frame. The bar 2 will thus be moved outwardly on arm 5a to a point which is further away from the shaft 6. At this point, the width of the arm 5a lying in the free part of the rectangular notch 20 is smaller due to the particular shape of said arm. Arm 5a will thus no more fill completely this cutout. The bar may thus move somewhat along the lengthwise direction thereof without moving the arm 5a. The further the bar 2 moves away from the shaft rod 6, the smaller is that portion of the arm 5a which lies in the cutout of the bar. The more this bar 2 moves away from the shaft 6, the smaller is the angle over which the arm 5a rotates during each alternating motion of, the bar. It may even happen that this part 5 will not rotate any more rotates during the alternating motion of the bar 2. If the part 5 moves less or not at all, the shaft 6 will rotate more slowly or it will stop. The rotating speed of the beam will consequently also be reduced. When in the case shown in the drawings, the element 23 moves nearer the element 22, the opposite will occur. The bar 2 will come nearer the shaft 6. By moving in this direction, the width of the arm increases. By coming nearer the shaft 6, the play between the bar 2 and the arm 5a decreases. The shaft 6 will thus rotate through a larger angle. The gear wheel 9 will thus also rotate over a larger angle for each reciprocating motion of the bar 2. The rotating speed of this wheel and thus of the beam 1 will be higher.

In that case where there is no warp shortening by the weft, the linear speed of the fabric passing over the pulling cylinder must be precisely the same as the speed of the warp passing over the thread-bearing roller. The linear speed measured on the circumference of the pulling cylinder must thus be the same as the linear speed on the circumference of the thread bearing roller. As mentioned above, the number of teeth of the sprockets l0 and 17, respectively, is equal to the number of centimeters in the circumference of the thread-bearing roller and of the pulling cylinder, respectively. As the links of the chains 11 and 18 are nearly the same, the teeth on the sprockets 10 and 17 are also the same. The ratio between the number of teeth of both these sprockets is thus equal to the ratio between the circumferences thereof. The ratio between the circumference of the sprocket 10 and the circumference of the sprocket 17 is thus equal to the ratio between the circumference of the thread-bearing roller and the circumference of the pulling cylinder. To make the linear speed of the warp passing over the thread-bearing roller equal to the linear speed of the fabric passing over the pulling cylinder, the linear speed of the chain passing over the sprocket 10 must thus be equal to the linear speed of the chain 18 passing over the sprocket 17. Indeed the ratio between the linear speed measured on the circumference of the sprocket l0 and the linear speed measured on the circumference of the threadbearing roller is equal to the ratio between the linear speed measured on the circumference of the sprocket 17 and the linear speed measured on the circumference of the pulling cylinder. As the sprocket formed by a part of the element 21 over which passes the chain 18 is identical with the sprocket formed by a portion of the element 23a over which passes the chain 11, the rotating speed of such sprocket 21 must thus also be equal to the rotating speed of the sprocket 23a to obtain the same linear speeds for both chains 11 and 18. Now this is perfectly made by the regulator. Indeed as soon as these two linear speeds are different, the rotating speed of the sprocket 21 will be different from the rotating speed of the sprocket 23a. Due to this last difference, the element 23 will move axially. The end of the lever 29 will influence the mechanism which rotates the beam 1. The linear speed of warp unwinding and thus the linear speed of chain 111 will change until the rotating speed of the sprocket 23a and which is driven by the chain is again the same as the rotating speed of the sprocket 21 which is driven by the fabric pulling cylinder 34.

In the more frequent case where there is a shortening of the warp, the linear speed of the fabric is smaller than the linear speed of the warp. For a particular pulling cylinder, such cylinder will have to rotate more slowly than in that case where there is no warp shortening. If a warp shortening of 2 cm. is obtained for one revolution of the pulling cylinder, it is necessary to arrange a sprocket 17 with two more teeth. Indeed, for each complete revolution, the pulling cylinder feeds 42 cm. of fabric. In that case where there is a warp shortening, it must feed 40 cm. of fabric during the same period of time, if of course the warp speed remains the same. Instead of making a complete revolution, the pulling cylinder will make only 40/42 revolution. To get such a result, as the linear speed of the chain 18 remains the same as in the case where there was no warp shortening, the circumference of the sprocket 17 must be larger by a ratio of 421 40. Thus, instead of having 42 teeth, the sprocket 17 should have 42 X 42140 teeth, that is to the nearest integer, 44 teeth. These last teeth must of course all be the same as the teeth used in that case where there is no warp shortening. There is thus obtained approximately 1 cm. more warp shortening to each pulling cylinder revolution by adding one additional tooth to the sprocket 17, in those cases where such warp shortening is not too large.

In any case, the same rotating speed is always obtained for the sprocket 21 and the sprocket 23a, thus the same linear speed for the chain 11 and the chain 18. With particular sprockets 10 and 17, one thus always obtains a constant ratio between the warp unwinding linear speed and the fabric winding linear speed. This ratio may be changed by replacing the sprocket 17 by a sprocket with another circumference and thus with another number of teeth. This ratio, for some particular pulling cylinder and thread-bearing roller, is determined by the warp shortening. The faster the shaft 19 of the regulator rotates and the more sensitive this regulator will be. This regulator does not cause any additional tension in the warp.

It must be understood that the invention is in no way limited to the above embodiments and that many changes may be brought therein without departing from the scope of the invention.

For instance, the above-described pawl may be comprised of two, four or some other number of separate parts which form as many pawls with different lengths and which are fixed on the same pivot-pin.

I claim:

1. A loom having: a warp letoff mechanism with a warp beam, a fabric takeup device with a pulling cylinder, a batten, a transmission positively driving said warp beam from said batten, and a regulator responsive to the difference between the speed of the thread being unwound from the warp beam and the speed of the pulling cylinder and acting on said transmission. t

2. A loom having a warp letoff mechanism with a warp beam and a thread-bearing roller, a sprocket on the threadbearing roller, a fabric takeup'device with a pulling cylinder, a sprocket on said pulling cylinder, a batten, a transmission positively driving said warp beam from said batten, and a regulator acting on said transmission and comprising: a support, a rotating shaft in said support, a sprocket fixed on said shaft, an element with a pin fixed on said shaft, 21 second element movable along and around said shaft and provided with a notch for said pin, said notch extending along a di ecgionat an angle-t o the axis of said shaft, a sprocket on said second-element. a

chain connecting the sprocket on said shaft with the sprocket.

on said pulling cylinder, a chain connecting the sprocket on said second element with the sprocket on said thread-bearing roller, and a lever transmitting the movement of said second element along said shaftto a control element of said transmission. 

1. A loom having: a warp letoff mechanism with a warp beam, a fabric takeup device with a pulling cylinder, a batten, a transmission positively driving said warp beam from said batten, and a regulator responsive to the difference between the speed of the thread being unwound from the warp beam and the speed of the pulling cylinder and acting on said transmission.
 2. A loom having a warp letoff mechanism with a warp beam and a thread-bearinG roller, a sprocket on the thread-bearing roller, a fabric takeup device with a pulling cylinder, a sprocket on said pulling cylinder, a batten, a transmission positively driving said warp beam from said batten, and a regulator acting on said transmission and comprising: a support, a rotating shaft in said support, a sprocket fixed on said shaft, an element with a pin fixed on said shaft, a second element movable along and around said shaft and provided with a notch for said pin, said notch extending along a direction at an angle to the axis of said shaft, a sprocket on said second element, a chain connecting the sprocket on said shaft with the sprocket on said pulling cylinder, a chain connecting the sprocket on said second element with the sprocket on said thread-bearing roller, and a lever transmitting the movement of said second element along said shaft to a control element of said transmission.
 3. The loom according to claim 2 in which said transmission comprises: a gear wheel on said warp beam, a rod with a threaded portion meshing with said gear wheel, a ratchet wheel on said rod, a part surrounding said rod and having a projection with a reduced width to its end, a pawl fixed by a pivot pin on said part and pulling against said ratchet wheel, and a bar rotatingly attached to said batten, said projection being anchored in a cutout of said bar, said lever having an end forming a two-pronged fork griping said bar. 